late notice

[Karen Barry <karen barry 2 bc edu>]

Boston College
Department of Physics
Colloquium


Nernst Effect and In-Plane Vortex-Like Excitations in Pseudogap Region 
of Cuprate Superconductors

Professor Hai-Hu Wen
National Lab for Superconductivity, Institute of Physics, Chinese 
Academy of Sciences
Beijing, China

Nernst effect has been measured for an underdoped and an optimally doped 
La2-xSrxCuO4 single crystal with the magnetic field applied along 
different directions. For both samples, when H || c, a significant 
in-plane Nernst voltage appears above Tc and keeps measurable up to a 
high temperature ( 100 K ) as reported earlier [ Nature 406, 486(2000) 
]. However, when H || a-b plane the Nernst signal along c-axis drops 
below the noise level quickly above Tc for the underdoped sample. This 
may suggest that the superconducting condensation is established 
simultaneously with the Josephson coupling ( or the coherent motion of 
Cooper pairs ) along c-axis. Moreover, the in-plane Nernst data with 
field at different angles shows a nice scaling behavior with the c-axis 
component of the field. All these give strong indications for strictly 
in-plane vortex-like excitations in the pseudo-gap region.
Thursday, November 6, 2003
4:00 p.m.
Seminar Room